Oak trees (Quercus spp.) as a source of extracts with biological activities: A narrative review

Abstract

Background: Oak trees (Quercus spp.) constitute a relevant source of fractions and ingredients that have been tested regarding their biological activities. The high number of species, varieties and materials that can be found through this genus has led to a great diversity of extracts that can be investigated regarding their potential to improve human health status. Scope and approach: In this review, several biological activities were revised through the scientific literature (antioxidant, immune-modulatory, antiproliferative, hypoglycaemic, hypocholesterolemic, antihypertensive, antimicrobial, etc.) paying attention to bioactive extracts obtained from different oak trees and parts, describing the selected extraction technology, the utilised experimental model, the published results and their potential impact on human health. Moreover, the related strengths and weaknesses were listed to elucidate the current state of the related scientific evidence. Key findings and conclusions: In vitro and in vivo analyses confirmed the potential of oak extracts particularly for antioxidant, anti-inflammatory, antitumoral and antimicrobial effects. However, some points must be further investigated: additional bioactive molecules and abilities testing, advanced extraction techniques evaluation and more animal studies and clinical trials to validate the mentioned activities when the extracts are included in food matrices.